A central part of the production of television broadcasts or the post processing of film material is video signal processing. The term video signal processing hereinafter denotes the switching and distribution of video signals from various sources such as, for example, television cameras or video recording apparatuses. Furthermore, the term denotes the combination of a plurality of signals by mixing, for it is also to be understood to mean the editing of recorded video material. For these purposes, production mixers and digital video effect apparatuses are predominantly used as the video signal processing device in production studios. The video processing apparatuses are used to generate a video output signal from a video input signal or from a plurality of video input signals in a controlled manner. In this case, a very significant part is played by trick generators for generating mixing effects. By virtue of the consistent use of large scale integrated components, modern mixers exhibit a plurality of independent mixing effect stages which can be used to represent diverse trick effects.
Mixers constructed in this way enable not only standard tricks such as rectangle, circle, fan, but also matrix tricks, NAM combination (“non additive mixing”) of two channels per trick generator, MIX combination (metamorphosis) and also special forms such as star, spiral, flower, fractals, and much more besides.
Despite all the diversity of tricks which can be realized in this way, their dynamic range is nonetheless restricted to mathematical manipulations of the underlying trick figures.
In addition to the mixing effects mentioned in the introduction, which are based on a modulation of the gating signals, EP 0 327 333 B1 proposes a further mixing effect based on an additional control signal being fed to the background color generator. The control signal is derived from the gating signal and effects a color transition from one side of the screen to the other.